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FROM VOLUME 4, NUMBER 10, OCTOBER 1991

PROFESSIONAL PUBLICATIONS...
MARINE CARBON AND FERTILIZATION

Item #d91oct29

"The Photolysis of Colloidal Iron in the Oceans," M.L. Wells (Darling Marine Ctr., Univ. Maine, Walpole ME 04573), L.M. Mayer et al., Nature, 353(6341), 248-250, Sep. 19, 1991. Laboratory results and optical modeling show that the photolysis of forms of solid iron may occur deep into the ocean's euphotic zone; the availability of iron to phytoplankton in the ocean may be much greater than previously thought.

Item #d91oct30

Two articles from: Nature, 353(6340), Sep. 12, 1991.

"Estimation of New Production in the Ocean by Compound Remote Sensing," S. Sathyendranath (Biol. Oceanog. Div., Bedford Inst. Oceanog., Box 1006, Dartmouth, N.S. B2Y 4A2, Can.), T. Platt et al., 129-133. An approach that depends on parameterizations developed from ship observations, as well as on satellite data, yields more representative estimates of the large-scale average new production than those calculated from ship data alone.

"Iron Still Comes from Above," a comment on the source of diatomic iron in the open ocean, p. 123.

Item #d91oct31

"Photochemical Degradation of Dissolved Organic Carbon and Its Impact on the Oceanic Carbon Cycle," K. Mopper (Rosenstiel Sch. Marine Sci., Univ. Miami, 4600 Rickenbacker Causeway, Miami FL 33149), X. Zhou et al., Nature, 353(6339), 60-62, Sep. 5, 1991.

Presents new data suggesting that the photochemical degradation of aquatic humic substances into biologically labile and/or volatile organic compounds is the rate-limiting step for the removal of a large fraction of DOC, and the rate will increase with increasing UV-B. Estimates the oceanic residence time of biologically refractory, photochemically reactive DOC to be 500-2100 years, less than its apparent 14C age.

Item #d91oct32

"Basin-Scale Estimates of Oceanic Primary Production by Remote Sensing: The North Atlantic," T. Platt (Biol. Oceanog. Div., Bedford Inst. Oceanog., Box 1006, Dartmouth, N.S. B2Y 4A2, Can.), C. Caverhill, S. Sathyendranath, J. Geophys. Res., 96(C8), 15,147-15,159, Aug. 15, 1991.

Coastal Zone Color Scanner data were combined with vertical profiles of chlorophyll and results of photosynthesis-light experiments, and used to test several different parameterizations necessary for calculating primary production. In some situations, less complete model versions gave results that differed by as much as 50% from the benchmark. Results suggest caution in using biomass as a proxy for primary production, especially outside the tropics. Remote sensing is the method of choice for calculating primary production at the ocean scale.

Item #d91oct33

"High Turnover Rates of Dissolved Organic Carbon during a Spring Phytoplankton Bloom," D.L. Kirchman (Marine Sci., Univ. Delaware, Lewes DE 19958), Y. Suzuki et al., Nature, 352(6336), 612-614, Aug. 15, 1991. High estimates of DOC concentrations and turnover rates based on North Atlantic data suggest changes are needed in models of carbon cycling and of the ocean's role in buffering increases in atmospheric CO₂.

Item #d91oct34

"Importance of Phaeocystis Blooms in the High-Latitude Ocean Carbon Cycle," W.O. Smith, Jr. (Dept. Botany, Univ. Tennessee, Knoxville TN 37996), L.A. Codispoti et al., ibid., 352(6335), 514-516, Aug. 8, 1991. Results suggest that the Greenland Sea may be a larger sink of atmospheric CO₂ than has been previously thought.

Item #d91oct35

"Top Predators in the Southern Ocean: A Major Leak in the Biological Carbon Pump," M.E. Huntley (Scripps Inst. Oceanog., Univ. California, La Jolla CA 92093), M.D.G. Lopez, D.M. Karl, Science, 253(5015), 64-66, July 5, 1991.

Although it has been suggested that primary production and carbon dioxide uptake of the Southern Ocean could be enhanced by the addition of iron, an analysis of the food web for these waters implies that they may be remarkably inefficient as a carbon sink. The large flux of carbon respired to the atmosphere by top predators, air-breathing birds and mammals, may transfer into the atmosphere as much as 20-25% of photosynthetically fixed carbon.

Item #d91oct36

Two articles from: Global Biogeochem. Cycles, 5(2), June 1991.

"Atmospheric Iron Inputs and Primary Productivity: Phytoplankton Responses in the North Pacific," R.W. Young (Dept. Marine Sci., Univ. S. Florida, St. Petersburg FL 33701), K.L. Carder et al., 119-134. Describes major increases in primary production following pulses of dust transported from Asia.

"Possible Effects of Iron Fertilization in the Southern Ocean on Atmospheric CO₂ Concentration," F. Joos (Phys. Inst., Univ. Bern, CH-3012 Bern, Switz.), U. Siegenthaler, J.L. Sarmiento, 135-150. Results from a high-latitude exchange/interior diffusion advection model show that the maximum atmospheric CO₂ depletion that would result from fertilization is 58 ppm after 50 years and 107 ppm after 100 years, with an uncertainty estimated to range from -29% to +17%. The possible effect of fertilization is small compared to CO₂ increases expected in the absence of strict control measures.

Item #d91oct37

"Low Iron Requirement for Growth in Oceanic Phytoplankton," W.G. Sunda (Beaufort Lab., Southeast Fisheries Ctr., Beaufort NC 28516), D.G. Swift, S.A. Huntsman, Nature, 351(6321), 55-57, May 2, 1991.

Found that an oceanic diatom was able to grow at a near maximum specific rate of about 1.0 per day at a cellular Fe:C ratio of 2 micro mol:mol, about 2-20% of values previously used to estimate algal Fe requirements in seawater. Results have important implications for iron limitation of primary productivity.

Item #d91oct38

"A Chemical Method for Estimating the Availability of Iron to Phytoplankton in Seawater," M.L. Wells (Darling Ctr., Univ. Maine, Walpole ME 04573), L.M. Mayer, R.R.L. Guillard, Marine Chem., 33(1-2), 23-40, Apr. 1991. A technique that employs the complexing agent 8-hydroxyquinoline (oxine) to measure a labile portion of total Fe in seawater appears to provide an operational method for estimating the biological availability of Fe in seawater.

Item #d91oct39

"Marine Biota Effects on the Compositional Structure of the World Oceans," H.S. Kheshgi (Res. Labs., Exxon Co., Annandale, NJ 08801), B.P. Flannery, M.I. Hoffert, J. Geophys. Res., 96(C3), 4957-4969, Mar. 15, 1991. The vertical structure of total carbon, alkalinity, nutrients and dissolved oxygen in the world oceans is examined with a 1-D box model of the equatorial and polar oceans.